The invention relates to a lining tube for producing a tubular liner for sewer pipe renovation work. The lining tube is comprised of at least one layer consisting of at least one resin-impregnated fiber band arranged in the form of a tube, and a tubular film located on the at least one fiber band.
Such a lining tube (liner) as well as a method for producing such a tubular liner are known from DE 4326503 C2, where a inner tubular film consisting of a band of foil material is wound on a winding mandrel, which in turn is then wound with resin-impregnated fiber bands. The number of fiber bands then determines the strength and the thickness of the later tubular liner and can be adapted in a suitable manner to the given case of application.
It is possible also to use a pre-extruded inner tube onto which the fiber bands can then be wound. Furthermore, an outer tubular film is applied to the outer side of the fiber bands. Such an outer tubular film is expected to assure superior handling of the tubular liner, on the one hand, and to protect the not yet cured resin against saponification as it is being pulled into a sewer pipe requiring renovation, on the other hand. This requires that the lining tube is adequately bonded to the resin-impregnated fiber material because as the tubular liner is being pulled into the sewer pipe, it is subjected to numerous stresses, for example stress caused by protruding edges, pieces of roots etc. A tubular liner pulled into a defective sewer pipe is caused to rest against the wall of the sewer pipe by means of pressure medium and the resin-impregnated fiber material is subsequently cured. Curing is carried out by means of different media depending on the type of resin employed. UV-curing is preferably employed at the present time.
Another problem consists in that because of fractured sites in the wall of the sewer pipe, or in the area of, for example house connections, the walls of the sewer pipe offer no adequate support when the lining tube is set up by means of a pressure medium. The walls of the lining tube therefore have to be adequately stable so that no excessive outward bulging and damages may occur in such cracked sites. For this reason, the fiber bands always have been wound until now with an adequate thickness in order to obtain adequate stability.
Now, the invention is based on the problem of providing a tubular liner of the type specified above with enhanced strength properties.
Said problem is solved according to the invention in that a plastic film employed for forming the tubular film has a reinforcement in the form of a layer of fleece laminated to the tubular film on the side facing the resin-impregnated fiber bands.
Owing to the fact that the layer of fleece is partly melted into the surface of the plastic foil due to the laminating process, it exhibits a similar expansion behavior. This provides a tubular film so wound with additional stability which, in the course of expansion of the tubular liner in the sewer pipe section represents an additional abutment that helps bridging cracked sites or house connection sections. It is possible in this manner to produce a much more uniform liner because when the tubular liner is set up, it will expand much more uniformly over the entire circumference. Furthermore the composite material comprised of the plastic film and the layer of fleece also offer the benefit that the bond into which the plastic foil enters with the resin, which is not a good bond per se, results in superior tie-up with the fiber band material. The resin penetrates the layer of fleece and thus enters into a very intimate and solid bond which makes it that much harder for the foil to be displaced especially as it is being pulled into the sewer pipe. This assures that the resin-impregnated fiber band material is always adequately covered by the outer plastic film and cannot come into contact with any residual water left in the sewer pipe sections. Moreover, the laminate is compressed in a superior manner, which results in a superior quality with respect to mechanical characteristics and in a uniform wall thickness of the cured tubular liner.
It has been found in tests that the layer of fleece may be preferably produced from a polyester material. Very fine and thin fleeces that are accessible to a laminating process can be produced from such a material.
Furthermore, it is possible also that the reinforced tubular film is surrounded by a outer tubular film consisting of at least one plastic foil. Such an embodiment permits allocating defined properties to the tubular film materials used. The plastic foil employed for producing the reinforced tubular film may then have corresponding strength properties, whereas the plastic film used for making the outer tubular film may have advantageous properties such as, for example opaqueness, impermeability to resin etc. as well. The outer tubular film can be produced in a wound manner or by one or several plastic films that are joined lengthwise along their edges. Of course, said properties can be assumed also only by the plastic film of the reinforced tubular film. The use of an additional tubular film, furthermore, offers the added advantage that the reinforced tubular film is not required to meet excessively high requirements with respect to tightness. In particular, films can be used that are laminated to a layer of fleece over their entire surface area.
It is possible to use a polyethylene sheet as the plastic film that offers both the properties required for the lamination process and the desired processing advantages. Such a material is advantageous also for the outer tubular film.
The fleece layer may be very thin, as a rule, in order to obtain the desired properties, so that the film so treated, furthermore, can be handled and wound onto the fiber tube with relative ease. It is favorable if the layer of fleece has a thickness of 10 to 250 xcexcm, preferably of 60 xcexcm.
According to the embodiment is it possible in this connection that the weight of the fleece layer amounts to 10 to 300 gram per square meter, preferably 30 grams per square meter. This clearly shows, furthermore, that the layer of fleece is relatively light in weight but nonetheless entirely adequate for satisfying the desired positive purposes.
It is possible also that the plastic film comprises a layer equipped as a diffusion barrier located on the side facing away from the resin-impregnated fiber bands. It is advantageous for safety and environmental reasons if the active resin ingredient is prevented from seeping into the soil in any case. A few favorably priced plastic foils do not represent any adequate diffusion barrier for the active resin ingredients, so that an additional layer is required.
Provision can be made for said purpose that the plastic film is a composite sheet material comprising a layer preferably consisting of polyamide (PA) serving as the diffusion barrier. Such composite foils can be produced in a very simple manner, for example by co-extrusion. The co-extrusion of polyethylene and polyamide, for example, can be carried out very easily in technical terms. No adhesion problems arise in connection with the adhesion of the PA-layer to the polyethylene sheet material.
Furthermore, the edge areas of the plastic film may not be laminated with a layer of fleece, whereby such edge areas are fused together with at least one plastic film for forming the tubular film.
As the foil laminated with a layer of fleece is being welded together, it is possible only with great difficulty that the marginal zones remain non-laminated. A permanent bond can then be produced by placing the non-laminated marginal areas one on top of the other and by subsequently welding them together. Even though it is conceivable that a tube produced in such a manner may be produced from one single web of sheet material by welding the marginal areas together, it is preferred that at least two bands of film material extending parallel with each other are correspondingly joined in their marginal areas.
The fiber bands may be advantageously impregnated with a UP-resin (unsaturated polyester) or VE-resin (vinyl ester). Said resins have been found to be highly successful in the field of application of the liners and provide for a good bond with the layer of fleece of the tubular film.
Furthermore, the invention concerns a tubular liner produced by curing from a lining tube. The tubular liner comprises a cured, shaped tubular layer of substance with embedded glass fibers and a plastic film solidly bonded to the surface of the layer of shaped substance. The side of the plastic film facing the layer of molded substance is provided with a reinforcement in the form of a layer of fleece laminated to the layer of molded substance. While the outer film with the layer of fleece is forming an abutment in the production of the tubular liner and offers advantages in this connection, the finished tubular liner has the advantage that a firm bond of the outer film to the fiber bands is assured.
The invention, furthermore, relates to a method for producing a tubular liner for sewer pipe renovation work. Resin-impregnated fiber bands are shaped for this purpose into a tubular body that is then surrounded by an outer tubular film. The resin-impregnated fiber bands are usually applied by means of a winding technique. In such a winding process, at least one resin-impregnated fiber band is wound around an inner tubular film mounted on a winding mandrel, and the outer surface is subsequently provided with an outer tubular film, which may be wound as well. In connection with the method as defined by the invention, a plastic sheet for producing the outer tubular film, which is provided with a layer of fleece laminated to it at least on the side later facing the resin-impregnated fiber bands, is wound onto the body of the tube. An application of a plastic film provided with a layer of fleece laminated to it has never been carried out until now in connection with tubular liners.
In another embodiment, a method for producing a tubular liner from a lining tube is provided in which the fleece laminated to the plastic film enters into a solid bond with the body of the tube as the latter is being cured to form a tubular body. After the primary strength of the lining tube has been produced by the cured fiber bands, and the supporting effect of the outer tubular film plays an only secondary role, what matters is then is an adequately solid bond between the plastic film and the fiber material in the final condition. The fleece has a positive effect in that regard for this purpose.